Placental tissue is normally discarded at birth, but is essentially a molecular time capsule for gene by environmental interactions and dysregulated molecular and cellular pathways that can be revealed at the level of the epigenome. Identifying epigenetic biomarkers at birth that reflect in utero exposures or predict adverse neurodevelopmental outcomes is an important goal that has been limited by prior technologies or lack of relevant tissue availability. Our team of currently collaborating interdisciplinary scientists within the Children?s Center for Environmental Health plans to use existing placental samples from a prospective high-risk cohort study (MARBLES) to identify epigenetic biomarkers at birth for in utero exposure to polychlorinated biphenyls (PCB) and neurodevelopmental outcomes by age three. Using unbiased whole genome bisulfite sequencing (WGBS), we have previously demonstrated that placental tissues retain the distinctive DNA methylation patterns of the preimplantation embryo and so can capture the molecular state in very early development, a feature that is conserved across mammalian species, including mouse. The new hypothesis to be tested in this proposal is that perinatal exposures to PCB adversely impact neurodevelopment and leave a lasting molecular signature over genes relevant to neurodevelopment that can be detected in placenta. The proposed PCB Epigenomic Brain & Behavior Lasting Effects Study (PEBBLES) will combine the analysis of human placental samples from the high-risk MARBLES cohort with the analysis of placenta and brain tissues and sorted cell types derived from a mouse model of perinatal exposure to the same mixture of PCB congeners detected in MARBLES mothers. This study will leverage existing neurological and behavioral analyses and samples to examine the relationship between PCB-induced perturbations of DNA methylation marks with adverse neurotoxic outcomes. Epigenomic analyses of placenta and brain as well as sorted cellular subtypes from each of these tissues will include WGBS for methylome, RNA-seq for transcriptome, and ATAC-seq for chromatin accessibility. Bioinformatic and statistical analyses will integrate the genomic data sets with behavioral and molecular outcome measures and determine whether similar epigenetic marks are observed in placenta that could be used to predict long-lasting adverse brain and behavioral outcomes in humans. !